Surface cleaning apparatus have been developed which include one or more cyclonic cleaning stages. Each cleaning stage may include a single cyclone, or a plurality of cyclones positioned in parallel. Typically, in cleaning stages comprising a single cyclone, a dirt bin is positioned below the cyclone. The cyclone has an outlet, which is in fluid communication with an inlet of the dirt bin. Typically, the dirt bin and the cyclone are coaxial. The inlet to the dirt bin comprises an opening centrally positioned in an upper surface of the dirt bin.
For example, U.S. Patent Application Publication 2006/0130448 to Han et al. discloses a cyclone having a cubic dirt bin. The dirt bin is centrally positioned below the cyclone, such that the dirt bin and the cyclone are coaxial. A dirt inlet is positioned at the centre of the upper square surface of the dirt bin, aligned with a dirt outlet of the cyclone.
U.S. Patent Application Publication 2006/0123590 to Fester et al. discloses a surface cleaning apparatus having a first cleaning stage including a single cyclone, and a second cleaning stage including a plurality of cyclones in parallel. The cyclones of the second cleaning stage are arranged annularly around the cyclone of the first cleaning stage. The dirt bin of the first cleaning stage is coaxial with the cyclone of the first cleaning stage, and extends outwardly such that a portion is positioned underneath the cyclones of the second cleaning stage. The dirt inlet to the dirt bin is annular, and is centered about the longitudinal axis of the dirt bin.